Mobile phones, cordless phones, portable game devices, personal digital assistants (PDA) and remote controllers each need a user interface in order to receive input from a user and to present information to the user. Remote controllers and cordless phones are typically stored in a household, while pagers, PDA devices and mobile phones are mobile devices which are typically made to be easily pocketable. However, mobile device that is well-suited for pocketing by a user is not large enough to house displays that are convenient for sustained use. A small display suffices well to check a phone number from a pager or to read a short message, but does not necessarily enable comfortable reading of web pages, for example.
Clam-shell formed mobile phones typically have a main display underneath a lid and a keypad on top of a body on which the lid rests when folded to a closed position. Hence, neither the keypad nor the main display is visible when the lid is closed. A secondary display is therefore often provided on the top of the lid in order to enable presenting of information while the lid rests on the body. A clam-shell form-factor thus prevents using a common display both in the closed and open configurations.
Sliding cover is an alternative to a clam-shell form factor. A slide enables maintaining a movable display visible to the user while exposing a keypad from underneath of the slide. Hence, a secondary display is not needed. However, mobile phones with slides do not expose the whole of the bottom part under the slide. Typically, a fully opened sliding cover still overlaps the body under the slide by more than one half of the length of the phone.